Laserfiche WebLink
<br />-33- <br />•The application includes same design information for the temporary diversion. <br />This information is sufficient to assess the feasibility of reclamation. <br />Dorchester has committed to supplying detailed designs in the future. The <br />reclamation bond held by the Division will be sufficient to cover the costs of <br />designing and reconstruct-ing this drainage. <br />The temporary diversion may be divided into three reaches; an upper, middle, <br />and lower reach. The upper reach is located in and adjacent to the Dorchester <br />Coal Mine permit area. It begins below the county road and continues to the <br />GEC property line. This reach of the diversion was approved as part of the <br />Dorchester Interim Permit. <br />Portions of this reach are cut into the base of a steep hillslope (the cut is <br />from a pre-law surface mine), and the stability of the hillslope may be <br />affected. Any mass wasting would reduce channel capacity. However, since <br />this diversion is only temporary, the operator will be able to perform any <br />necessary maintenance. Following the cessation of operations, the diversion <br />would be backfilled, thus stabilizing the adjacent hillslope. <br />The middle reach of the Magpie Creek diversion was constructed at a later time <br />by GEC Minerals, Inc. This reach crosses the Dorchester -GEC permit boundary <br />connecting the Dorchester diversion with an unnamed tributary to Magpie <br />Creek. This reach consists of two segments, a steep transition and a designed <br />• channel between the transition and the GEC haul road. <br />~~ The lower reach of the diversion follows the course of an unnamed tributary of <br />Magpie Creek to again join Magpie Creek downstream of the GEC Mining <br />operation. This part of the diversion is not designed and the original <br />channel was not modified to accommodate the additional streamflow. <br />Examination of this reach of channel in the field showed the channel to <br />contain durable gravel and boulders, and several sections appeared to be <br />bedrock-controlled. For this reason, the lower reach of the channel would not <br />be expected to undergo significant bank erosion or channel degradation during <br />the relatively short period of time that the temporary diversion would remain <br />in place. <br />The Division finds the operation to be in compliance with the requirements of <br />this section. <br />XYII. Backfilling and Grading - Rules 2.05.3(6)(b), 2. <br />The course of the reconstructed Magpie creek drainage would cross the <br />backfilled mine portals for the Dorchester No. 1 mine. Seepage from the <br />stream system might enter the underground workings, increasing the potential <br />for degrading the water entering adjacent ground water systems and decreasing <br />downstream flow. However, these potential adverse effects could be avoided by <br />adequately sealing the mine portals to the flow of water. The operator has <br />• provided a detailed portal seal configuration that wil] minimize recharge to <br />the mine from the stream. <br />